A model of resonance energy transferring among Ti3+ ions in Ti:A12O3 crystal was setup according the Dexter theory of sensitization luminescence, from with the critical distance Rc of Ti3+ ions were estimated, between which concentration quenching could take place and the correspondent doping concentration Nc. By the comparison with the measured spectra data, obvious concentration quenching has not been observed even if the doping level reaches 1.28×1020 cm-3 (or 0.38wt%).